If you want to see if there are any routers advertising IPv6 prefixes on your LAN, and if so, what IPv6 prefix they are advertising, you can use the tool 'rdisc6'.
Usage is easy:
rdisc6 -1 -r1 -q wlan0
Output is for example
$ rdisc6 -1 -r1 -q wlan0
So, a good first check of your router.